Because I have a high ELI reading with my TT earthing - around 620 ohms
- I want to drive in some new copper rods to see if I can improve it. My
question is about the size of the cable from the rods back to the CU. I
know that 10mm would be ideal, but because I have a 50 metre reel of
6mm, and I would have to buy in some 10mm, I would prefer to use that.
The run back to the MET would be about 6 to 7 metres, so would the 6mm
be acceptable?

Eddy Current wrote:

Because I have a high ELI reading with my TT earthing - around 620 ohms
- I want to drive in some new copper rods to see if I can improve it. My
question is about the size of the cable from the rods back to the CU. I
know that 10mm would be ideal, but because I have a 50 metre reel of
6mm, and I would have to buy in some 10mm, I would prefer to use that.
The run back to the MET would be about 6 to 7 metres, so would the 6mm
be acceptable?

Yes.
2.5mm is acceptable if it is not buried, and protected from corrosion
and mechanical damage.
So 6mm is fine if not buried, and protected from corrosion.

I'd always go for the 10mm, as, well, it just looks 'safer' as it is a
fatter cable! Also, I dont keep 6mm cable.
The differences in impedance in that short run is very small, so a fault
will take maybe a millisecond more to trip the RCD. In real life, there
will be no measureable difference.

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To reply by e-mail, change the ' + ' to 'plus'.

On 02/02/2013 18:48, A.Lee wrote:
Eddy Current wrote:

Because I have a high ELI reading with my TT earthing - around 620 ohms
- I want to drive in some new copper rods to see if I can improve it. My
question is about the size of the cable from the rods back to the CU. I
know that 10mm would be ideal, but because I have a 50 metre reel of
6mm, and I would have to buy in some 10mm, I would prefer to use that.
The run back to the MET would be about 6 to 7 metres, so would the 6mm
be acceptable?

Yes.
2.5mm is acceptable if it is not buried, and protected from corrosion
and mechanical damage.
So 6mm is fine if not buried, and protected from corrosion.

I'd always go for the 10mm, as, well, it just looks 'safer' as it is a
fatter cable! Also, I dont keep 6mm cable.
The differences in impedance in that short run is very small, so a fault
will take maybe a millisecond more to trip the RCD. In real life, there
will be no measureable difference.


Many thanks for that.

On Sat, 02 Feb 2013 18:09:00 +0000, Eddy Current wrote:

Because I have a high ELI reading with my TT earthing - around 620 ohms
- I want to drive in some new copper rods to see if I can improve it. My
question is about the size of the cable from the rods back to the CU. I
know that 10mm would be ideal, but because I have a 50 metre reel of
6mm, and I would have to buy in some 10mm, I would prefer to use that.
The run back to the MET would be about 6 to 7 metres, so would the 6mm
be acceptable?

Any reason not to run two bits of 6mm side by side?

Cheers

Dave R

On 02/02/2013 20:10, David.WE.Roberts wrote:
On Sat, 02 Feb 2013 18:09:00 +0000, Eddy Current wrote:

Because I have a high ELI reading with my TT earthing - around 620 ohms
- I want to drive in some new copper rods to see if I can improve it. My
question is about the size of the cable from the rods back to the CU. I
know that 10mm would be ideal, but because I have a 50 metre reel of
6mm, and I would have to buy in some 10mm, I would prefer to use that.
The run back to the MET would be about 6 to 7 metres, so would the 6mm
be acceptable?

Any reason not to run two bits of 6mm side by side?

Cheers

Dave R


Interesting idea, I'll certainly consider that. Many thanks.

On Saturday, February 2, 2013 6:09:00 PM UTC, Eddy Current wrote:
Because I have a high ELI reading with my TT earthing - around 620 ohms

- I want to drive in some new copper rods to see if I can improve it. My

The run back to the MET would be about 6 to 7 metres, so would the 6mm
be acceptable?

6mm is overkill, and fine


NT

On Feb 2, 8:53*pm, wrote:
On Saturday, February 2, 2013 6:09:00 PM UTC, Eddy Current wrote:
Because I have a high ELI reading with my TT earthing - around 620 ohms

- I want to drive in some new copper rods to see if I can improve it. My
The run back to the MET would be about 6 to 7 metres, so would the 6mm
be acceptable?

6mm is overkill, and fine

NT

I was a bit concerned by the electrician that came to do the wiring of
my PV panels who expressed concern at my earth having 98 ohm
resistance - "Yes, it's TT; and thanks for confirming that it is as
low as that!".. Puzzled look, followed by "Is that the size of your
earth wire - it should be 10mm" -- "and what would the point of that
be when it's feeding into 98 ohms?". Went away grumbling.

Rob

On 02/02/2013 18:09, Eddy Current wrote:
Because I have a high ELI reading with my TT earthing - around 620 ohms
- I want to drive in some new copper rods to see if I can improve it. My
question is about the size of the cable from the rods back to the CU. I
know that 10mm would be ideal, but because I have a 50 metre reel of
6mm, and I would have to buy in some 10mm, I would prefer to use that.
The run back to the MET would be about 6 to 7 metres, so would the 6mm
be acceptable?

The various combinations of requirements are summarised he

http://wiki.diyfaq.org.uk/index.php?...o_your_ear th




--
Cheers,

John.

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On 03/02/2013 01:08, John Rumm wrote:

The various combinations of requirements are summarised he
http://wiki.diyfaq.org.uk/index.php?...o_your_ear th

Yes and note that 10 mm^2 isn't mentioned.

The most common situation is that insulated single wire (6491X) will be
used as the earthing conductor, and will be buried for some of its
length. The PVC insulation gives corrosion protection, but not
mechanical protection. Therefore the correct size to use for most TT
installations is 16 mm^2.

--
Andy

In article ,
says...

The various combinations of requirements are summarised he

http://wiki.diyfaq.org.uk/index.php?...o_your_ear th


Note there is a broken external link to an IEE Wiring Matters article in
that.

The article in question is contained in this:

http://electrical.theiet.org/wiring-...6/complete.cfm

--

Terry

On 04/02/2013 11:02, Terry Casey wrote:
In article ,
says...

The various combinations of requirements are summarised he

http://wiki.diyfaq.org.uk/index.php?...o_your_ear th


Note there is a broken external link to an IEE Wiring Matters article in
that.

The article in question is contained in this:

http://electrical.theiet.org/wiring-...6/complete.cfm

Thanks, I have updated the link.


--
Cheers,

John.

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| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
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